For providing depth information of an object, X-ray stereo imaging is used, for example in medical imaging. However, it has been found that, although stereo imaging provides useful depth information, the user, for example a physician, maintains and sometimes even prefers monoscopic viewing techniques. The switching to stereo imaging is hence sometimes avoided. Thus, additional depth information is sometimes not made visible to the user. US 2010/0067662 describes a stereo rotating anode X-ray tube.